This application seeks support for the first Translational Cerebellar and Midbrain-Hindbrain Developmental Malformation Meeting, to be held in Washington, DC on Oct. 15-16, 2005. Disorders involving the development of the human cerebellum and midbrain-hindbrain have suffered from a lack of uniformity in clinical, radiographic and molecular classification, and a lack of adequate animal models to probe molecular and developmental underpinnings or to develop potential therapeutic interventions. In the last several years, however, there have been major advances in the understanding of these conditions, with the proposal of new clinical entities, new systems for patient classification and the cloning of the first several genes for these human conditions. However, the lack of uniformity in diagnosis, the rarity of genetically informative families for study, and the dearth of appropriate animal models has significantly hampered progress in this area. This is an optimal time to bring together the key participants in these advances, to help overcome these hurdles. The meeting proposes to bring together clinical and basic science researchers studying cerebellar and midbrain-hindbrain malformations, to align the field in the direction of understanding of key mechanisms. It will serve as a forum to build consensus regarding the diagnosis of these important clinical entities, to standardize diagnostic and imaging protocols for proper phenotyping, to build collaborations among clinician researchers that will advance gene identification, and to develop appropriate animal model counterparts of these conditions. We propose to host a two-day meeting with emphasis on four major areas: clinical advances, radiographic advances, molecular advances, animal model advances. The meeting will address the major subgroups of these conditions, including Dandy-Walker malformation, Joubert syndrome, pontocerebellar hypoplasia, isolated cerebellar hypoplasia and combined cerebellar and cortical hypoplasia. This application at the invitation from three NIH branches, and with matching financial support from patient support groups and a private donor, highlighting the importance of this meeting to the public. The information content will be made available on the Internet. Thus this Meeting will serve as a resource for both the scientific and lay community throughout the world.